Kbase 15579: ISDN - What is it ? Integrated Services Digital Network
| Autor |
Progress Software Corporation - Progress |
| Acesso |
Público |
| Publicação |
10/05/1998 |
|
ISDN - What is it ? Integrated Services Digital Network
ISDN (Integrated Services Digital Network) is a network routing
system based on the public digital phone network. Generally to
use it you have to have a contract with your local supplier
(Usually telephone company) and necessary hardware and software.
There are basically 2 major types of connection: ISDN card
on a computer or ISDN router on a network. ISDN cards usually
have device drivers that make them look like a normal network card
to the networking software running on the box. ISDN router is just
what the name says, a router between 2 or more networks.
ISDN makes the physical connection on need basis and drops it
usually after a certain timeout. This line drop, however does not
show to the high-level network applications because the hw/sw
fools any keepalives to think that the line still is active.
The line is reconnected as soon as any real data is to be
transmitted over again. The connection delay in ISDN is very low
(Fractions of second) so end user usually does not even notice it.
The way ISDN works is highly tunable to suit into different
situations. Some hw/sw even have a possibility to enter in local
line charges (Call initiating charge, charges per minute over
various times etc.) and they adjust the way they open/close the
real line accordingly.
To Progress and other high-level applications all this should be
transparent, meaning that our software does not know nor care what
happens underneath as long as the underlying infrastructure works
correctly. There have been bad examples of ISDN over time but it is
slowly getting to be reliable and usable transport medium.
--
22.03.1996
Progress Software Technical Support Note # 15579